 Not according to Science News, which reported on researchers at Vanderbilt University who are developing small, portable air samplers that can be carried by mail trucks, bicycle couriers, or police walking their beats to give us much more accurate local readings. Fitted with a GPS chip, each device knows precisely where it is, and if an extensive network of them can be established, it could prove extremely useful in sniffing out dirty air and identifying specific pollutants where we actually breathe them.